Each year roughly 200,000 patients are diagnosed with brain tumors in the United States. Roughly 17,000 of these tumors are “benign,” meaning that the tumor mass is not cancerous. However, the other roughly 183,000 of these tumors are “malignant” (i.e., cancerous), meaning that they are capable of causing or contributing to patient death. Approximately 10% of cancerous brain tumors are “primary” tumors, meaning that the tumors originate in the brain. The primary tumors typically consist of brain tissue with mutated DNA that aggressively grows and displaces or replaces normal brain tissue. The most common of the primary tumors are known as gliomas, which indicate cancer of the glial cells of the brain. In most instances, primary tumors appear as single masses. However, these single masses can often be quite large, irregularly-shaped, multi-lobed and/or infiltrated into surrounding brain tissue.
Primary tumors are generally not diagnosed until the patient experiences symptoms, such as headaches, altered behavior, sensory impairment, or the like. However, by the time the symptoms develop the tumor may already be large and aggressive.
Various treatments for brain tumors exist and several involve accessing the brain so that treatment of the tumor can be effected. One such method of treatment involves the treatment of tumors by “heat” (also referred to as hyperthermia or thermal therapy). In particular, it is known that above 57 C all living tissue is almost immediately and irreparably damaged and killed through a process called coagulation necrosis or ablation. Malignant tumors, because of their high vascularization and altered DNA, are more susceptible to heat-induced damage than normal tissue. Various types of energy sources may be used, such as laser, microwave, radiofrequency, electric, and ultrasound sources. Depending upon the application and the technology, the heat source may be extracorporeal (i.e. outside the body), extrastitial (i.e. outside the tumor), or interstitial (i.e. inside the tumor).
Interstitial thermal therapy (ITT) is a process designed to heat and destroy a tumor from within the tumor. One advantage of this type of therapy is that the energy is applied directly to the tumor rather than passing through surrounding normal tissue. Another advantage of the type of therapy is that the energy deposition is more likely to be extended throughout the entire tumor.
One exemplary ITT process involves the use of laser (LITT) and begins by inserting an optical fiber into the tumor, wherein the tumor has an element at its “inserted” end that redirects laser light from an exterior source in a direction generally at right angles to the length of the fiber. The energy from the laser thus extends into the tissue surrounding the end or tip and effects heating. The energy is directed in a beam confined to a relatively shallow angle so that, as the fiber is rotated, the beam also rotates around the axis of the fiber to effect heating of different parts of the lesion at positions around the fiber. The fiber can thus be moved longitudinally and rotated to effect heating of the lesion over the full volume of the lesion with the intention of heating the lesion to the required temperature without significantly affecting tissue surrounding the lesion.
To locate the tumor or other lesion to be treated with LITT, magnetic resonance imaging is frequently used. Although these imaging systems have been helpful to assist the surgeon in determining a location of the lesion to be treated, an instrument for determining the trajectory for entry of the optical fiber into the brain is necessary in order to ensure controlled accuracy in treating the tumor. Several conventional methods and apparatuses are used to determine trajectory so that surgical and observational instruments may be inserted in the patient's brain.
Stereotactic neurosurgery is a field of neurosurgery in which a probe is advanced through a burr hole to a target of interest by means of a mechanical device attached to the skull with aiming based on pre-operative images. The probe may be a biopsy needle or an implantable device, but it is geometrically rigid, so that its tip can be brought to a target of interest specified on a pre-operative image, by means of a geometrical calculation. For the past decade, the field has been advancing from the imposition of large, classical metal frames, which encompass the entire head of a patient, to the attachment of small platforms placed only over an entry site to reduce patient discomfort, facilitate surgical access, allow multiple targeting during one surgery via multiple platforms, and reduce procedure time, while maintaining the same level of accuracy.
Classical metal frames are designed for approaching one target at a time with an unrestricted entry point towards the deep target by employing the principle that the target is at the center of a sphere. Because of the long trajectories, both accuracy and patient comfort are challenged by the demands of surgeries for deep brain stimulation (DBS) in which the patients are awake throughout the lengthy surgery procedure (about 5-8 hours).
During the last few years, microplatforms have become available as replacements for the classical frames for DBS stereotactic surgery.
U.S. Pat. No. 6,206,890 to Truwit discloses an apparatus for aligning the trajectory of, guiding, and introducing and withdrawing a surgical probe to treat a brain tumor. The apparatus includes a unitary base which has a ball joint member that is movably attached to the base. The ball joint member has a passage therein which forms a portion of the trajectory path. The ball joint member also includes a long, cylindrical, thin-walled guide stem which has an opening therein that substantially aligns with the passage in the moveable member. The ball joint member includes either an integral guide stem for holding the positioning stem or a removably attached guide stem. In the case of the former, a positioning stem is inserted into the opening of the guide stem for purposes of trajectory alignment. In the case of the latter, the removably attached guide stem can be removed and replaced with a positioning stem.
However, there are problems regarding geometric stability, limited space for access to the burr hole and surgical manipulation once the tower is mounted, the time consuming process of aiming, and the difficulty of locking on the target. Access to the burr hole is crucially important for the purpose of stopping bleeding from the bone cavity, dura, and the surface of the cortex during the procedure. Aiming is achieved by watching a guiding icon on the screen of the intraoperative tracking system, while adjusting the orientation of the platform. When the icon indicates a correct trajectory, the platform must be locked into place with one hand, while it is held at the correct trajectory with the other. The trajectory is two-dimensional, meaning that there are two mutually perpendicular angular adjustments required, each of which must be set simultaneously for the correct trajectory. Finding the correct trajectory via the guiding icon is time consuming because of the difficulty of making fine adjustments of one angle of the approach without changing the other angle. A further difficulty with this aiming procedure is maintaining both angles of the correct trajectory while locking the device on target. The locking step can be especially frustrating, because, if either angle is changed inadvertently during locking, as revealed by the guiding icon, the device must be unlocked and the adjustment started from the beginning. Typically several iterations are required, resulting in wasted operating time.
U.S. Pat. No. 7,167,760 to Dawant et al. discloses a device that also requires the attachment of bone-implanted fiducials and the subsequent acquisition of a preoperative tomogram, but it does not require intraoperative optical tracking for aiming. Instead the device is custom made for each patient based on a pre-operative tomogram and the surgeon's identification of the entry point and the target on that tomogram. Thus, the device arrives at the operating suite pre-aimed with no adjustment required intraoperatively. It is a one-piece rigid plastic block having a cylindrical hole that accommodates the probe, supported by a plurality of legs, each of which attaches to a base that is implanted in the skull. Fiducial markers are attached to these same bases before the pre-operative image is acquired and discarded after imaging. The shape of the device provides far greater access to the burr hole but does not allow the surgeon total flexibility in changing trajectory. In addition, while the device is disposable a significant disadvantage is that the patient must wait between the acquisition of the tomogram and the delivery of the device which can range from two to four days.
U.S. Patent Publn. 2007/0106305 attempts to address the shortcomings of the Dawant device by disclosing a surgical platform that includes a ring structure and a ball joint that is configured to be received in the ring structure, where the ball joint defines a bore for accommodating a surgical probe therethrough. The surgical platform includes a plurality of threadably-adjustable leg assemblies. While the adjustable legs provide the surgeon with the ability to make macro and micro adjustments, mechanically the device is cumbersome to use.
Therefore, a heretofore unaddressed need exists to establish a rigid, secure apparatus for holding a long cylindrical medical device in a fixed, three-dimensional trajectory relative to the patient, that is able to withstand torquing, bumping and other potentially dislodging or disorienting forces during patient transfer from the operating room to the MRI suite and while in the MRI suite during the procedure. A further need exists that will give the surgeon complete maneuverability to easily and quickly make macro changes or fine adjustments to the trajectory; to change the position of the medical device when desired and as needed in the MRI; and to visualize the surgical site. The device must be MRI-compatible, lightweight and able to be easily affixed to the patient. The maneuverability allows the surgeon to drill multiple holes.